Sometimes it fetches few events, sometimes none. Log from akonadiconsole:

> akonadi_davgroupware_resource_10 (0x28545a0) 47 { Command: "FetchCollections" Collections: "UID 21" Depth: "0" Resource: "akonadi_davgroupware_resource_10" Mimetypes: "()" Ancestors Depth: "2" Ancestors Attributes: "QSet()" Enabled: "false" Sync: "true" Display: "false" Index: "false" Status: "false" }
akonadi_davgroupware_resource_10 (0x28545a0) 47 { Response: "FetchCollections" Error Code: "0" Error Msg: "" ID: "21" Name: "https://server.com/remote.php/caldav/calendars/bit/default/" Parent ID: "19" Remote ID: "https://server.com/remote.php/caldav/calendars/bit/default/" Remote Revision: "" Resource: "akonadi_davgroupware_resource_10" Mimetypes: "(application/x-vnd.akonadi.calendar.todo, application/x-vnd.akonadi.calendar.event, inode/directory)" Statistics: { Count: "-1" Unseen: "-1" Size: "-1" } Search Query: "" Search Collections: "QVector()" Cache Policy: { Inherit: "true" Interval: "60" Cache Timeout: "-1" Sync on Demand: "false" Local Parts: "(ALL)" } Ancestors: { { ID: "19" Remote ID: "akonadi_davgroupware_resource_10" Name: "akonadi_davgroupware_resource_10" Attributes: "QMap()" } { ID: "0" Remote ID: "" Name: "" Attributes: "QMap()" } } Attributes: "QMap((AccessRights, a)(ENTITYDISPLAY, ("default" "" "" ()))(ctag, http://sabre.io/ns/sync/1)(davprotocol, 0))" Display: "Undefined" Sync: "Undefined" Index: "Undefined" Enabled: "true" Virtual: "false" Referenced: "false" }
akonadi_davgroupware_resource_10 (0x28545a0) 47 { Response: "FetchCollections" Error Code: "0" Error Msg: "" ID: "-1" Name: "" Parent ID: "-1" Remote ID: "" Remote Revision: "" Resource: "" Mimetypes: "()" Statistics: { Count: "-1" Unseen: "-1" Size: "-1" } Search Query: "" Search Collections: "QVector()" Cache Policy: { Inherit: "true" Interval: "-1" Cache Timeout: "-1" Sync on Demand: "false" Local Parts: "()" } Ancestors: { } Attributes: "QMap()" Display: "Undefined" Sync: "Undefined" Index: "Undefined" Enabled: "true" Virtual: "false" Referenced: "false" }
> akonadi_davgroupware_resource_10 (0x28545a0) 48 { Command: "FetchCollections" Collections: "UID 21" Depth: "0" Resource: "" Mimetypes: "()" Ancestors Depth: "2" Ancestors Attributes: "QSet()" Enabled: "true" Sync: "false" Display: "false" Index: "false" Status: "false" }
akonadi_davgroupware_resource_10 (0x28545a0) 48 { Response: "FetchCollections" Error Code: "0" Error Msg: "" ID: "21" Name: "https://server.com/remote.php/caldav/calendars/bit/default/" Parent ID: "19" Remote ID: "https://server.com/remote.php/caldav/calendars/bit/default/" Remote Revision: "" Resource: "akonadi_davgroupware_resource_10" Mimetypes: "(application/x-vnd.akonadi.calendar.todo, application/x-vnd.akonadi.calendar.event, inode/directory)" Statistics: { Count: "-1" Unseen: "-1" Size: "-1" } Search Query: "" Search Collections: "QVector()" Cache Policy: { Inherit: "true" Interval: "60" Cache Timeout: "-1" Sync on Demand: "false" Local Parts: "(ALL)" } Ancestors: { { ID: "19" Remote ID: "akonadi_davgroupware_resource_10" Name: "akonadi_davgroupware_resource_10" Attributes: "QMap()" } { ID: "0" Remote ID: "" Name: "" Attributes: "QMap()" } } Attributes: "QMap((AccessRights, a)(ENTITYDISPLAY, ("default" "" "" ()))(ctag, http://sabre.io/ns/sync/1)(davprotocol, 0))" Display: "Undefined" Sync: "Undefined" Index: "Undefined" Enabled: "true" Virtual: "false" Referenced: "false" }
akonadi_davgroupware_resource_10 (0x28545a0) 48 { Response: "FetchCollections" Error Code: "0" Error Msg: "" ID: "-1" Name: "" Parent ID: "-1" Remote ID: "" Remote Revision: "" Resource: "" Mimetypes: "()" Statistics: { Count: "-1" Unseen: "-1" Size: "-1" } Search Query: "" Search Collections: "QVector()" Cache Policy: { Inherit: "true" Interval: "-1" Cache Timeout: "-1" Sync on Demand: "false" Local Parts: "()" } Ancestors: { } Attributes: "QMap()" Display: "Undefined" Sync: "Undefined" Index: "Undefined" Enabled: "true" Virtual: "false" Referenced: "false" }

Lines prepended with ">" were in red so i guess they must be errors.

Reproducible: Always

Steps to Reproduce:
1. In akonadiconsole add "Dav groupware resource"
2. Point said resource to your nextCloud (ownCloud) instance which has calendar app enabled and contains some events. 
3. Uncheck "limit caldav retrieval time range"
3. Let it synchronize.

Actual Results:  
Only 0-3 events are fetched. Successfully fetched event count is different if resource is removed and re-added. It never fetches more than few events out of tens of events i have.

It does properly fetch contact birthdays.
Sometimes it also fetches contacts (CardDav), sometimes it does not fetch any.

Expected Results:  
It should fetch events of entire calendar.

Version is 16.08 (it is not in version selector for some reason)